Even if children have a weak immune system and are prone to inffections, it is considered physiological for them to have lymphocytosis. What is the reason for this?
Such type of relative lymphocytosis may be due to:
1)vaccinations in children
Vaccinations increase the number and the types of antigens available to the developing T-cells for their central tolerance.
Thymus is the centre for central tolerence of the T-cells.The T-cells are so important for the immunity in children because they (memory T-cells)can also trigger the formation of B-cells for humoural immunity.
2)Thymus activity which is at peak during the period from childhood to puberty.[REFERENCE]